let fs = require("fs");
fs.stat("1.txt",(err,stat)=>{
  if(err){
    console.error("出错啦~")
  }else{
    console.log(stat)
    console.log(stat.mtime.constructor)
    console.log(stat.mtime.toGMTString())
  }
})
/*
 {
  dev: 578915258,
  mode: 33206,
  nlink: 1,
  uid: 0,
  gid: 0,
  rdev: 0,
  blksize: undefined,
  ino: 14355223812315852,
  size: 17,
  blocks: undefined,
  atimeMs: 1537520879646.8403,
  mtimeMs: 1537520879648.3398,
  ctimeMs: 1537520879648.3398,
  birthtimeMs: 1537520879646.8403,
  atime: 2018-09-21T09:07:59.647Z,
  mtime: 2018-09-21T09:07:59.648Z,
  ctime: 2018-09-21T09:07:59.648Z,
  birthtime: 2018-09-21T09:07:59.647Z }
 * */